Adjustable electrode assembly for high-frequency heating systems



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Sept. 30, 1952 H, R, WARREN 6142595 ADJUSTABLE ELECTRODE ASSEMBLY FOR HIGH-FREQUENCY HEATING SYSTEMS 5 Sheets-Sheet 2 Filed Feb. 12, 1948 |9A WA INVENTOR.

ENRY R. WARREN ATTORNEYS Sept. 30, 1952 H, R, WARREN 2,612,595

ADJUSTABLE ELECTRODE ASSEMBLY FOR HIGH-FREQUENCY HEATNG SYSTEMS Filed Feb. 12, 1948 5 Sheets-Sheet 5 .IN V EN TOR.

HENRY R. WARREN BY v Preferably', the conveyorv grounded. To insure that the conveyor remains' total width, each of pins 2| will be lifted and each stop I9 suitably positioned on its channel I 1. The pins will then be released for movement into engagement with its rack 22. While boards are being placed in position, the racks and each stop I9 will be moved by cam r1-A away from stops I9 and then released, as shown in Fig. 6, for application of the force of the spring 23 to the boards to hold them tightly together and against the stationary stops i f Quickly to set or harden or dry the adhesive,

high-frequency electrical energy is applied tothe clamped boards or work I0. An upper, adjustable-.electrode 29 is connected by a flexible conductor Sil-and a conductor 3I into, and forms a part of, the output circuit of a high-frequency generator which includes a vacuum tube 32. The high-frequency oscillator includes a grid coil or inductor 33, a grid resistor 34 and by-pass condenser 35, a source of anode supply indicated by B-plus and B-minus. Included in the anode circuit is a high-frequencychoke coil 3S, a blocking capacitor'31 being connected between the anode Iand the tank coil or inductor 39. The conductor 3 I` is-connected by way of a vacuum condenser 39 to the upper end of the tank coil 38, while the lower encll thereof is connected to ground and to the cathode of the tube 32. A substantial part of the capacitance of the tank circuit appears-between the adjustable electrode 29 and ground.

at substantially ground potential it is desirable to include between conveyor supporting channels or `as a whole isv I-bealns 49 and 4I` a plate 42, Fig. 2, connected Y toground and in length and breadth substantially corresponding with the length and breadth ofthe supporting channelsl beneath the adjustable electrode 29. The plate 42 capacitively couples channels I1 to ground in event of 4poor electrical contact between the channels I1, the chainj links I3 and the I-beams 49 and 4I. The high-frequency generator preferably supplies high-frequency electrical energy at a frequency ofthe order of 1,000,000 cycles per second to 30,000,000 cycles per second, though the particular frequency utilized is not critical and may be of above or below the indicated range.

Thechannel members I1 provide a grid support for the-boards or work I0, that is a support characterized by a plurality of supporting surfaces spaced one from the other lengthwise of the conveyor II. Similarly, the adjustable electrode 29 isf a grid-like character. It comprises, Fig. 6, a plurality of mechanically interlocked, sliding or telescoping tubular members. In the preferred form of the invention, elements 45, rods or tubes,

ofsmaller diameter alternate lengthwise ofthe` conveyor with tubular elements 49 of larger di-ameter slidably to receive members 45. members or elements and 46 together form an array of cylindrical electrode elements disposed inspaced relation along a planesubstantially parallel to the channels I1 and the work or boards I0 supported thereon. The elements at one side of the electrode 29, as Viewed in Fig. 3,

are preferably electrically and mechanically secured to a conducting and supporting member 41 as by screws 48. The conducting member 41 is in turn secured to a plate49., Similarly, the elements on the opposite side of the electrode 29 are secured to a conductingmember 59' as by screws 5I, the member 50 being in turn secured to a plate 52. By moving one set of electrode elements toward or away from the other set of electrode elements the'effective width of the electrode may be adjusted for the most desirable width with reference to the number of boards or the width of the work I0 to be heated. Further, by alternately disposing the elements 45 and 46, a substantially uniform field is maintained between the electrode 29 and the conveyor II for all widths of electrode 29, any effect on the eld of `the difference of thediameter of the elements 45 Vand 46 having thus been eliminated. The elements 45 and 46 are mechanically/'interlocked in sliding relation in the sense that they mutually support each other. l Further in Iaccordance with the present invenf tion, the electrode elements on the lefthand side of the electrode 29, as viewed in Fig. 2, are maintained relatively stationary, and the entire ad' justment of the width of electrode 29 islmade by -adjusting the righthand elements. This is ac-` complished in connection with the parallelk motion links provided for movement of the elec-rk trode 29 as awhole to increase and decrease'the distance between it and the work I0. Fromthe plates 49 and 52 there extend four sets of insulators respectively numbered 53-56. These' insulators serve as means to suspendnthe electrode 29 from their supporting structures comprising four links 58-6I, all four of which fractionally appear in Fig. 6. As best shown in Figs. 1 and 2, it will be observed that each link may be in the form of a turnbuckle for adjustment of its lengthj from a stationary structure 62 which may be a part of the frame, not shown. The ylinks 58-GI are preferably adjusted to be of equal length and to support the electrode 29 in a plane parallel to' that of the bedplate or platform formed by 'conveyor II and'parallelto the plane of the boards I0 supported thereby.v By making the links of equal length, the electrode 29 may be swung as by means of Aa cord 63 to increase the distance between electrode 29 and the work I0. The links of Yequal length maintain the electrode parallel to the Work I9, and in any position to which it may be swung it remains parallel to any other position thereof. The cord 63 may be of insulat-` ing material or it may be of conductive material f such' as a flexible steel cabley or wire. vThe cord or cable 63 may be wound on a drum 64 either by a motor or by a crank 65, with insulators interposed between it and its coupling member 63-A. It will be seen that the lower ends of the links', 58-6I are pivotally connected to rods G6 and 61 which extend through channel members secured to the insulators. Specifically, the strut onrod 66 extends through the channel members E8 and 69 associated'with insulators 55 and 53, while the rod 61 extends through the `channel members 1Dk and 'II associated with the insulators 54 and 59.

, It will be observed, Figs.' 2 and 6, that one side The tubular of the electrode 29 is anchored in fixed position by collars or-locknuts 12 and 13, while the other side thereof isfree to slide along the arms of the triangular structure formed by the rods 66 and 61. q Additionally, to prevent lateral movement ofy the electrode 29 a strut 14, Fig. 2, extends from a point adjacent the upper stationary pivot'15 of thelinki-BB down 'to the movable electroni-eend .of the link 60. The upper end of the strut14 is preferably held in place by means of a pair of locknuts 16, while a similar pair oi locknuts 11 secures the lower end to the lower threaded part ofthe turnbuckle-link 60. A similar strut 18, in like manner, cooperates withthe rod 61 to. form a second triangular structure to brace the other end of the electrode 29 against lateral movement and .preclude transverse swinging of electrode I I. One of the locknuts 19 which securesthe lower end of .thefstrut 18 tok they electrode end of the link 6I appears in Fig. 1. The upper end of strut 18 is held in fixed position by locknuts 80 on link 59. The arrangement is such that the4` concurrent :pivotal or swinging movement of each link is maintained parallel to the other links and each is restricted to a plane perpendicular to and longitudinal of the plane of the supporting surfaces of the conveyor I I. Conducting member 41 is supported by insulating means 55 and 56 which are atcorrespondin'g or like apexes of the two triangular structures formed by the struts and links.

It is to be further understood that the stationary stops I8 as rwell as the adjustable stops I9 are provided with rounded corners to minimise corona effects and resultant arcingL which would tend to occur if metallic structure subjected to the high-frequency eld had sharp or pointed edges or projections. In this connection, it will'be further observed that the out-turned ends I1-A, Fig. 4of each of the channels provide a greater area than would be the case if simple U-shaped channels were utilized without the out-turned ends. tric field will be more uniform throughout the area of electrode 29 by reason of the outwardly turned' projections I1.A on each of the channel members I'I. v

Further to minimize possibilities of arcing, the pendulantly lmounted links 69 and 6I are so located that one side of lthe electrode 29 is spaced inwardly from the path taken by the stops I8. similarly, it will 'be observed in Fig. 2 that the electrode 29 has been so adjusted that the righthand end of electrode 29 is spaced inwardly from the adjustable stops I9. This spacing need not be very great, .preferably of the order of from 1/2 to 2", but will b e adequate to minimize, if not entirely eliminate, 'arcing between the projecting members. It is to be further understood that for loads of any selected width, the foregoing minimum spacingwillV be maintained by proper adjustment of the width of electrode 29.

Adjustment of the width of electrode 29 is readily accomplished by an operator who by grasping theconducting member 5U or 52 may slide the elements attached to it into and out of the elements attached tothe stationary conducting member 41. By anchoring the stationary member 41 orv bracing it against lateral movement, such an operator can make all of the adjustments from one side of the conveyor which, it will be` understood, will ordinarily be of substantial length for accommodation of boards of the order of -or 20.feet long, or more. By so adjusting the width of the electrode in relation to the width of the work, the high-frequency heating equipment will be. more efficiently utilized. The iiexibility of operation is greatly increased by reason of the adjustability of electrode 29. By adjusting the electrode area to bevvery nearly equal to thearea of the load,-the maximum amount of circulating current will pass through the load and a minimum through the air. Thus;

In other words, the electhegpower kfactor will be higher and the gena erator will deliver ,an increased iormaximum amount of power to the load. This means higher conveyor speeds for a given rate ofheating. Thus, maximum eiciency is realized. Y,

In operation of the high-frequency generator, the electrode 29 serves further important functions. As well understood by those skilledin the art. vacuum tubes, such as the tube 32, when includedin oscillator circuits, have greatly shortened lives unless they are protected against excessive internal dissipation of energywhich occurs when the tube output is small. VIn accordance with the present invention, not only is that protection neatly afforded but also meansnecessary for controlling the loadingare provided. More particularly, between the electrode 29 and the work l0 there is4 an air space. In effect, there aretwo capacitors in series, one including as the dielectric thereof the aforesaid air space and Athe other including asthe dielectric thereof thev load comprising the adhesively coated boards I0. With the oscillator in operation, it will be understood lthat as the air gap is increased the voltages across these two capacitors vary inversely with their capacitances. The greater the air gap, the greater will be the voltage across it and the less will be the voltage across the load or boards I0.

From the standpoint of the oscillator tube 32, for an increasing air gap the load willvdecrease and the plate dissipation thereof will rise. 'Conversely, as the kelectrode 29 is'moved nearer the load l0, the voltage applied to the load increases. The load on the oscillator or high-frequency generator also increases, but so long as the load is within the rating ofthe tube the plate dissipation will not be excessive. Accordingly,` by rotating` the crank 65 the electrode 29 may' be swung about its pendant links which, while maintainingelectrode 29 parallel to the conveyor and the boards I0, move it toward or away from it to'increase or decrease the air gap or the spacing therebetween. This adjustmentmay be made with reference to any vsuitable load-indicating means, suchA as "an ammeter 8i included in the direct-'current anode circuit of tube 32.

It is to be further observed that the foregoing method of controlling the? load on the oscillator 32 is highly desirable forthe reason that there are no losses inthe air gapand thus the adjustment of the electrode 29 toward and away from the work represents an eilicient means of adjusting thev voltage applied to the glue lines lof the boards being heated. i I n changing from the gluing or bonding of a lessernumber of boards tot a larger number of boards, or vice versa, it will be seen that the effectiv'earea ofv the electrode 29 will be increased or decreased. Accordingly, the capacitance between the electrodes connected to the high-frequency generator will change.l The corrective adjustment, then necessary, will be made by operation of the crank 65 to change the position of the electrode 29.

Though any suitable high-frequency generator may be utilized, a generator of theA type diagrammatically shown in Fig. 1 is preferred for the reason that the frequency-determiningl circuit, the tank circuit, includes the total capacitance between the electrodes, that of the vacuum conn denser 39, and the inductance of the' tank inductor 38; that is to say, upon movement of the electrode'29 toward or away from the conveyor I I,l

theresultant change in capacitance will change: the resonant frequency of the tank circuit, How-F- 7 vr, tlie excitation ofthe: gridf derived directly fromthe tankv circuit, through the inter-electrode capacity, will cause the oscillator to operate at a new frequency. The load-tank-circuit will at all times be resonant to the generatorl frequency, since it is the frequency-determining circuit of the generator.

The condenser 39 has been described as of the vacuum type and this type of capacitor is prefer-red for the reason that in one preferred embodiment of the invention the capacitance of the condenser 39 was high, of the order of 100 micromicrofarads, the capacitance between the work electrodes being of the order of 500 micromicrofarads.

While a preferred form of the inventionhas been described, it is to be understood that further modifications may be made within the scope of the appended claims. For example, the inner sliding members of the electrode 29 may be either tubular or solid. In general, the outer tubes preferably have thin walls. If for large widths of electrode 29, the walls for structural reasons must be of substantial thickness, it will be desirable to bevel the ends of the larger tubes 46 in avoidance of sharp corners. Though cylindricalelements are preferred, a pair of flat conducting sheets, mechanically interlocked and slidable with respect to each other, may be'utilizedvin place-of the cylindrical elements 45 and 4B. The electrode 29 as a whole may-beV useful in applications-other than with a conveyor ofthe type described. For example, the conveyor I I, by reason of the plurality of channelmembers I'I, providas/,al grid-like electrode beneath the grid-like electrode 29. While the conveyor II is provided for movement of the boards or work I beneath the electrodes during heating, it will be obvious that the adhesive-setting heating operation can be carried out with the work and grid structure of the lower electrode stationary. With the conveyor arranged, Fig. 1, to move work from right to left beneath electrode 29, it will be observed that in the event the electrode 29 is engaged by any work carried by the conveyor, such engagement will cause the electrode to swing about its pivotal mounts. The effect istwo-fold. First, it avoids the jamming of the work between the conveyor and the electrode and it simultaneously reduces the intensity of the electric field applied to the work. When the work or boards are progressively moved between the electrodes the conveyor will preferably be provided with means for automatically feeding the boards into and out of it. For example, in Fig. 6 it will be observedrthat the rollers'26 on the extensions 22-A of each of the racks 22 engage a stationary cam surface 21 which moves the rack.22 and the movable stops I9 to release the spring pressure on the boards. Such a releasing mechanism is preferably actuated at or prior to the time the channel member I'I in moving from right to left starts downward around the sprocket wheel I4', Fig. 1.

A similar cam adjacent the opposite end of the conveyor maybe provided to hold'the movable clamp in a releasing position until after insertion of the boards and will be so shaped as to permit each spring 23 gradually to move each clamp I9 against the boards. As further shown in Fig. 6, an opposing thrust cam 82 may be -pro-v vided opposite the cam 2'I. A roller 83; shown enlarged in Fig. 5, is pivotally carried at the end of each channel member and engages the surface, 82 toicounteractthe thrustdeveloped by 'the movement of: eachv roller 28 .towardthezcrest ofthecam 21.1 'f

Inzthcevent. an arc-should occur betweenone of thetransverse elementsofzthe-upper electrode 29andthe-work I0', the movement therebeneath of the workzby the conveyor- I I produces continuous lengthening ofrthe arc until extinguishmen't thereof. The-lower electrodeinthe formA of the invention shown: iny the drawings comprises the conveyor; II havingv the transverse members; I.1 spacedr along :and driven by theidriving links, I3 ofi-the endlessl chains I2.. Since the transverse members I'I move relative to the, upper. elements of electrode 29; therewillv beilengtheningand extinguishment' ofiany; arc whichV mayform between oneiof4 the upperrtransverse elements and onerof the moving lower elements,- they direction of-movement of the;latter. being in a direction normalv to the transverse; or longitudinal.- axes thereof.'

What: is claimed is:v

1. Inga high-frequency heating j apparatus, the combination of a rstelectrode having a relatively large` area and a second cooperating adjustableielectrode of relatively large area extending in parallel relation to said rst electrode and comprising a plurality of telescoping outer and inner elements spaced one from the other throughout the length of said second electrode, said outer elements at one side of said electrode alternating with the inner elements with; the same regularity as at the opposite side to mini.- mize distortion of said electric eld due to the larger diameters of said outer elements, said outer and inner elements being slidable one within the other for adjustment of one dimension of said second electrode to correspond with a similar dimension of work to be subjected to a high-frequency eld.

2. An adjustable electrode for cooperation with a stationary electrode of a high-frequency heating apparatus comprising a pair of conducting members spaced one from the other, a stationary support, a plurality of conducting elements spaced one from the other and electrically connected to said members and extending from one of said members to the other, a plurality of links pivoted at corresponding'endsrespectively to said adjustable electrode and to said stationary support for supporting said adjustable electrode for swinging movement about the pivotal axes of said links, said links being arranged to maintain the plane of said adjustable electrode generally parallel to said stationary electrode when swung relative to said stationary electrode, and means for swinging said adjustable electrode about said pivotal axes bodily to move it lengthwise of said stationary electrode to adjust the spacing between said adjustableelectrode and said stationary electrode.

3. An adjustable electrode for cooperation with an adjacent electrode of a high-frequency heating apparatus comprising a pair of conducting members spaced one from the other, electrically conductive elements disposed in mechanically interlocked sliding relation one to the other, vsaid conducting members supporting the outer endportions of said elements, a plurality of pivoted links for" supporting said electrode for pivotal movement, said links being arranged to maintain the plane of said electrode generally 4parallel to said 'f adjacent electrode during pivotal movement thereof, and means for pivotally moving said 'electrodeto adjust the spacing'b'etween aic adjustable electrode and said adjacent elec- 9` '4. In a dielectric heating'system havinga'rst electrodefor work which is to be subjected-to a high-frequency electric lfield, the combination of a lsecond cooperating electrode, means suspending said "second electrode above 'and 'generally parallel 'to said rst electrode, saidmeans including a pluralityof links which cooperate to maintain said second electrode parallel to said rst electrode during pivotal movement of said second" electrode, said second electrode being made up of a plurality of conducting elements spaced one from the otherlthroughout the length of said second electrode and disposed in sliding relation one to the other forladjustment of the effective area thereof, and -means for pivotally moving said second electrode to vary the spacing between said first and second electrode.l

for support of work to be heated, a cooperating `5."Inr a dielectric heating system havinga flatr the-spacing between it and said platform while maintaining said electrode substantially parallel to said platform thereby uniformly to change throughout the effective area of saidelectrode the intensity of the high-frequency electric field applied to the work, said electrode being madeup of a plurality of telescopingfouter andv inner elements "spaced one from the other throughout the' length of said electrode, said outer elements at one side of said electrode alternating with inner elements with the same regularity as at thefopposite side to minimize distortion of said electrioiield due to the larger diameters of said outer elements, said outer and inner `elements being'fi'slidable one Within the other for adjustmentof the effective area of said electrode to correspond with the area of the work to be subjected to said high-frequency field.

6. In a dielectric heating system having a at platform for the support of work which is to be subjected' to a high-frequency electric field, the combination of means including ran electrode for applying a high-frequency eld to said Work, means suspending said electrode above and generally parallel to said platform, said suspending means including pivoted links of substantially equal length for mounting said electrode, means for effecting concurrent swinging movement of said links and of said electrode to change the spacing between it and said platform while maintaining said electrode substantially parallel to saidy platform thereby uniformly to change throughout `the eiective area of vsaid electrode thek intensity of the high-frequency electriciield applied to the work. l

4 ,7. A dielectricheating systemincluding a bedplate of. substantial area for supportingwork to be heated and a cooperating, movable electrode comprisinf:r a plurality of conducting elements disposed'A parallel to said bedplate and in spaced relationl one to the other,;pivoted links mounting said movable electrodeabove and parallel t said bedplate, and meansy for bodily swinging both saidlinksgand said movable electrode toward and away from said bedplate by rotation of said piv-l oted links and bylateral movement of said movable electrode to vary the spacing therebetween. 8. A dielectric heating system including a bed trode substantially parallel to said bed for uni" form change throughout the efiective area of said electrode of `the'inter'isity of'the high-.freev quency electric eld applied to the work. I

9. In a dielectric heating system having acon-` veyor for transporting work through a high-frei quencyelectric rleld, the combination of a cooperating electrode, means including a pluralitylzof; links suspending 'said electrode: above and generally parallel to saidconveyor, means for swing-- ing saidelectrode with said links away froiniand in the direction of travelof said conveyor-gandmeans iorming triangularstructures with'fsaidr links to preclude transverse swingingnof saldiA electrode, said electrodebeing made lip of' coni-14v ducting elements disposed in sliding relation'one to the lother "and spaced 'one fromy 'the .other throughout the length of said electrode for'rv d.

justment of the effective area thereof."

10. In a dielectric heating system having a con;l veyor fortransporting work through a high-free? quency veld, the combination of a cooperating? electrode, means including a plurality ofV vlinks* ,otally' supported'at one'end thereof for "penduelantly suspending v'said movable `electrode Aabove and generally parallel tofsaid rst'electrodef means for'swinging said movable electrode withsaid links toward and Vaway from said rst'electrodev to change the spacingtherebetween, a strut interconnecting the pivotally supportedendjof one link andthe lelectrode "end of another link to prevent movement thereof in any directionv other than pivotal movementin a plane; and aI strut interconnecting the electrode ends of saidlinks.

' 12.111 a dielectric heating system having a' iirst electrodefor the support 'of Work which is to 'be-I subjected to a high-frequency elect-riciield,'the combinationfof` a second electrode, means .including links supporting said secondelectrode above;

and parallel to" saidrst electrode, means 'fr swinging said second electrode with slaidilinks toward and away from, said rlrst electrode to vary thev intensity of" the high-frequency `elec-" tric' neldthrebetween, struts forming triangular shaped structures vWith said links, and rnpeansginl` sulating 'saidsecond electrode fromlsaidmlinks', saidsecond electrode being made upv of conduct`A ing elements disposed in slid-ing relationoie t6 the other, a conducting member supported by insulating means associated with like apexes of said triangular structures and supporting one end of each of said sliding members, a conducting member supported by insulating means movable in one direction with respect to said firstnamed insulating means and supporting the other end of each of said sliding members for adjustment of one dimension of said electrode.

I3. In a high-frequency heating system, an electrode having relatively slidable members, a supporting framework for said electrode including pivoted links permitting swinging movement of said electrode about the pivotal axis of said links to. an adjusted position, structural members rigidly interconnecting said links to precludemotion of said links transversely of aforesaid swinging movement, and means adjustably attaching said slidable members to said framework to permit their relative sliding movementk ina .direction transversely of said swinging movement.

14. In a dielectric heating system having a rst electrode for the support of work which is t be subjected to a high-frequency electric field, the' combination of a second electrode made up of a plurality of conducting elements disposed in telescoping relation one to the other for adjustment of the width thereof, conducting members supporting one end' of each of said conducting elements, means including a plurality of links supporting said second electrode above and parallel to said iirst electrode, struts forming triangular shaped structures with one of said links, insulating means rigidly secured at one apex of said triangular shaped structure and supporting one of said. lconducting members at one side of said second' electrode, and insulating means slidably mounted on a side of said triangular shaped structure. supporting the other conducting memf tierl at the other side of said second electrode for adjustmentof the distance between said conductingrelements thereby to change, the Width of said secondielectrode.

115. In a dielectric heating system havinga grounded electrode for the support of Work which isto be subjected to a high-frequency electric field', the combination of a cooperating electrode, suspension means including a plurality of links suspending said electrode above and generally parallel to saidy grounded electrode, struts; forming triangular structures with said links which cooperate to maintain said second electrode parallel'to. said grounded electrode during pivotal movement` of' said links, said second electrode being made up of at. least two conducting elements disposed in overlapping sliding relation one. to the other, said suspension means including' means for securing one of said elements to said: triangular structures, and means for slidably supporting the other of said elements from at, leastone arm of said triangular structures for yadjustment of one element lengthwise of the other'element.

16. In a high-frequency heating system having a, conveyor electrode for the support of work to be conveyed through and subjected. to a highfrequency electric eld and a second electrode disposed in cooperating relation with said con-- veyor electrode, suspensionl means pivotally sus-` pending said second electrode for swinging movement toward and away from said conveyor electrode while parallel thereto, means for bodily adjusting the position of said second electrode by swinging it about its pivotal suspension to change its spacing relative to work on said conveyor, said suspension means permitting said. second electrode to swing away from said work in the direction of travel of said conveyor electrode in event of engagement. by said work during travel between said electrodes to avoid jamming, and simultaneously to reduce the intensity of the electric fieldapplied to said work.

17. In a high-frequency heating system, the combination` of means including a rst electrode and; a second electrode spaced therefrom for conveying work between them for application to the work of a high-frequency electric field throughout the travel of the work between said electrodes, suspension means pivotally suspending said secondy electrode for swinging movement toward and away from said first electrode while parallel thereto, means for bodily adjusting the position of said second electrode by swinging it about its pivotal suspension to changeits' spacingl relative to the work' between said electrodes, said suspension means permitting said second electrode to swing away from said. work in ther direction of travel thereof between. said. electrodes.

18. In a high-frequency heating system, the combination of a conveyor electrode having a plurality of transverse conducting members spaced one from the other for the support of' Workk to be conveyed thereby, a second electrode spaced from said iirst electrode and work supported thereby for application to the work of a highfrequency electric eld, said second electrode comprising a plurality of transverse conducting elements spaced one from. the other, and means for driving said conveyor electrode for movement;v of work between said electrodesin a direction generally' normal to the longitudinal axes; of said transverse elements and of said transversemembers, said movement lengthening and ythereby* extinguishing any arcs which form between a` moving transverse conducting. member and av relatively stationary transverse conducting element.

HENRY R. WARREN.

REFERENCES CITED They following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 894,070. Schwerin July 21 1908 1,876,106 Usselman Sept. 6, 1932 1,875,360 Taylor Sept. 6, 1932 1,900,573 McArthur Mar. 7, 1933 1,998,332', Page Apr. 16, 1935 2,288,269. Crandell June 30, 1942 2,317,281 Linquist Apr. 30, 1943. 2,319,174 Wilson May 11, 1943 2,428,615 Brown Oct. 7, 1947 2,442,986 Ransburg June 8, 1948 2,457,659 Graham et al. .Dec. 28, 1948 2,491,687 Nutt Dec. 20, 1949 2,521,808 Taylor Sept. 12, 1950 FOREIGN PATENTS Number Country Date 229,416 GreatBritain Feb. 26, 1925 OTHER REFERENCES Moran et al.: Modern Plastics, June 1944', page 118. 

